Accurate leveling is one of the most important procedures in many civil engineering works and machinery installations, such as the selection of ground level surface, the mounting of templates, the building of brick walls, the paving of tiles, the building of interior partitions, the mounting of ceiling boards, and the installation of large-dimension machine tools, cranes, automatic conveyors, etc. Accurate leveling is an important basis to secure good quality and safety in many engineering works.
Conventionally, the principle of using a floating air bubble is applied to the leveling. A round tubular leveling means is used to find a leveled surface by visually determining whether an air bubble in the tubular leveling means is at a balanced position. Or, in an even simpler manner as shown in FIG. 1, a hose filled with water can be utilized to achieve such purpose by holding two ends thereof until the water surfaces at two ends of the hose reach the same level. There are many shortcomings existed in the above-described conventional leveling methods, such as:
1. The hose method can not be used to measure the level of two distantly spaced points and therefore has limited function. The leveling by visually determining the balanced position of an air bubble in a tubular leveling means is not always accurate. PA1 2. To calibrate or adjust the position of the level itself, several adjusting screws attached thereto must be rotated to correct the inclination of the level itself until the air bubble in the level is visually determined to be at a balanced position. A user would usually require a substantial amount of time to complete this correction or adjustment procedure by finely turning the adjusting screws, one by one, while no one can assure a satisfactory result will be obtained. This procedure greatly and adversely affects the efficiency of the leveling.